The Tranisiting Dust of Boyajian's Star

From May to October of 2017, Boyajian's Star displayed four days-long dips in observed flux, which are referred to as “Elsie,” “Celeste,” “Skara Brae,” and “Angkor” (Boyajian et al. 2018). This Elsie family dip event was monitored with the Las Cumbres Observatory in three bands, B, r', and i'. Looking at each dip individually, we analyze the multi-band photometry for wavelength dependency in dip depth to constrain properties of the transiting material. We find that all of the dips show non-grey extinction and are consistent with optically thin dust. Interpreting the dips as transiting dust clouds, we constrain the properties of the dust grains and find that the average grain radius is <1 micron, assuming silicate composition. This wavelength dependency and grain size is inconsistent with observed properties of the long-term “secular” dimming (Meng et al. 2017), suggesting that the dust causing the dips is from a separate population.